/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun<iot25@lingyun>
 *                  All rights reserved.
 *
 *       Filename:  epoll.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(13/03/25)
 *         Author:  LingYun <iot25@lingyun>
 *      ChangeLog:  1, Release initial version on "13/03/25 20:12:39"
 *                 
 ********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <time.h>
#include <pthread.h>
#include <getopt.h>
#include <libgen.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/epoll.h>
#include <sys/resource.h>

#define MAX_EVENTS 512
#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))

static inline void print_usage(char *progname);
int socket_server_init(char *listen_ip, int listen_port);

void set_socket_rlimit(void);

int main(int argc, char **argv)
{
	int listenfd, connfd;
	int serv_port = 0;
	int daemon_run = 0;
	char *progname = NULL;
	int opt;
	int rv;
	int i, j;
	int found;
	char buf[1024];
	int epollfd;
	struct epoll_event event;
	struct epoll_event event_array[MAX_EVENTS];
	int events;

	struct option long_options[] =
	{ 
		{"daemon", no_argument, NULL, 'b'},
		{"port", required_argument, NULL, 'p'},
		{"help", no_argument, NULL, 'h'},
		{NULL, 0, NULL, 0}
	}; 
	progname = basename(argv[0]);

	/*  Parser the command line parameters */
	while ((opt = getopt_long(argc, argv, "bp:h", long_options, NULL)) != -1)
	{ 
		switch (opt)
		{ 
			case 'b':
				daemon_run=1;
				break;
			case 'p':
				serv_port = atoi(optarg);
				break;
			case 'h': /*  Get help information */
				print_usage(progname);
				return EXIT_SUCCESS;
			default:
				break;
		} 
	} 

	if( !serv_port )
	{ 
		print_usage(progname);
		return -1;
	}
	set_socket_rlimit(); /*  set max open socket count */

	if( (listenfd=socket_server_init(NULL, serv_port)) < 0 )
	{
		printf("ERROR: %s server listen on port %d failure\n", argv[0],serv_port);
		return -2;
	}
	printf("%s server start to listen on port %d\n", argv[0],serv_port);

	/*  set program running on background */
	if( daemon_run )
	{
		daemon(0, 0);
	}

	if( (epollfd=epoll_create(MAX_EVENTS)) < 0 )
	{
		printf("epoll_create() failure: %s\n", strerror(errno));
		return -3;
	}

	//event.events = EPOLLIN|EPOLLET;
	event.events = EPOLLIN;
	event.data.fd = listenfd;

	if( epoll_ctl(epollfd, EPOLL_CTL_ADD, listenfd, &event) < 0)
	{
		printf("epoll add listen socket failure: %s\n", strerror(errno));
		return -4;
	}

	for ( ; ; )
	{
		/*  program will blocked here */
		events = epoll_wait(epollfd, event_array, MAX_EVENTS, -1);

		if(events < 0)
		{
			printf("epoll failure: %s\n", strerror(errno));
			break;
		}
		else if(events == 0)
		{
			printf("epoll get timeout\n");
			continue;
		}

		/*  rv>0 is the active events count */
		for(i=0; i<events; i++)
		{
			if ( (event_array[i].events&EPOLLERR) || (event_array[i].events&EPOLLHUP) )
			{
				printf("epoll_wait get error on fd[%d]: %s\n", event_array[i].data.fd, strerror(errno));
				epoll_ctl(epollfd, EPOLL_CTL_DEL, event_array[i].data.fd, NULL);
				close(event_array[i].data.fd);
			}

			/*  listen socket get event means new client start connect now */
			if( event_array[i].data.fd == listenfd )
			{
				if( (connfd=accept(listenfd, (struct sockaddr *)NULL, NULL)) < 0)
				{
					printf("accept new client failure: %s\n", strerror(errno));
					continue;
				}

				event.data.fd = connfd;
				//event.events = EPOLLIN|EPOLLET;
				event.events = EPOLLIN;

				if( epoll_ctl(epollfd, EPOLL_CTL_ADD, connfd, &event) < 0 )
				{
					printf("epoll add client socket failure: %s\n", strerror(errno));
					close(event_array[i].data.fd);
					continue;
				}

				printf("epoll add new client socket[%d] ok.\n", connfd);
			}
			else /*  already connected client socket get data incoming */
			{

				if( (rv=read(event_array[i].data.fd, buf, sizeof(buf))) <= 0)
				{
					printf("socket[%d] read failure or get disconncet and will be removed.\n",
							event_array[i].data.fd);

					epoll_ctl(epollfd, EPOLL_CTL_DEL, event_array[i].data.fd, NULL);
					close(event_array[i].data.fd);
					continue;
				}
				else
				{
					printf("socket[%d] read get %d bytes data\n", event_array[i].data.fd, rv);

					/*  convert letter from lowercase to uppercase */
					for(j=0; j<rv; j++)
						buf[j]=toupper(buf[j]);

					if( write(event_array[i].data.fd, buf, rv) < 0 )
					{
						printf("socket[%d] write failure: %s\n", event_array[i].data.fd, strerror(errno));
						epoll_ctl(epollfd, EPOLL_CTL_DEL, event_array[i].data.fd, NULL);
						close(event_array[i].data.fd);
					}
				}
			}
		} /*  for(i=0; i<rv; i++) */
	} /*  while(1) */
CleanUp:
	close(listenfd);
	return 0;
}

static inline void print_usage(char *progname)
{
	printf("Usage: %s [OPTION]...\n", progname);

	printf(" %s is a socket server program, which used to verify client and echo back string from it\n",
			progname);
	printf("\nMandatory arguments to long options are mandatory for short options too:\n");

	printf(" -b[daemon ] set program running on background\n");
	printf(" -p[port ] Socket server port address\n");
	printf(" -h[help ] Display this help information\n");

	printf("\nExample: %s -b -p 8900\n", progname);
	return ;
}

int socket_server_init(char *listen_ip, int listen_port)
{
	struct sockaddr_in servaddr;
	int rv = 0;
	int on = 1;
	int listenfd;

	if ( (listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
	{
		printf("Use socket() to create a TCP socket failure: %s\n", strerror(errno));
		return -1;
	}

	/*  Set socket port reuseable, fix 'Address already in use' bug when socket server restart */
	setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
	memset(&servaddr, 0, sizeof(servaddr));

	servaddr.sin_family = AF_INET; 
	servaddr.sin_port = htons(listen_port);

	if( !listen_ip ) /*  Listen all the local IP address */
	{
		servaddr.sin_addr.s_addr = htonl(INADDR_ANY); 
	}

	else /*  listen the specified IP address */
	{

		if (inet_pton(AF_INET, listen_ip, &servaddr.sin_addr) <= 0)
		{
			printf("inet_pton() set listen IP address failure.\n");
			rv = -2;
			goto CleanUp;
		}
	}

	if(bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0)
	{
		printf("Use bind() to bind the TCP socket failure: %s\n", strerror(errno));
		rv = -3;
		goto CleanUp;
	}

	if(listen(listenfd, 64) < 0)
	{
		printf("Use bind() to bind the TCP socket failure: %s\n", strerror(errno));
		rv = -4;
		goto CleanUp;
	}

CleanUp:
	if(rv<0)
		close(listenfd);
	else
		rv = listenfd;
	return rv;
}

/*  Set open file description count to max */
void set_socket_rlimit(void)
{
	struct rlimit limit = {0};

	getrlimit(RLIMIT_NOFILE, &limit );
	limit.rlim_cur = limit.rlim_max;
	setrlimit(RLIMIT_NOFILE, &limit );

	printf("set socket open fd max count to %d\n", limit.rlim_max);
}
